The present invention relates to a new and improved construction of a control arrangement for a gear testing machine.
Generally speaking, the control arrangement for a gear testing machine of the present development is of the type comprising a slide or carriage system supporting a measuring feeler and possessing a measuring drive which can be regulated by a velocity regulator. A lever system which is actuated by the slide system serves for moving a generating straight edge upon which rolls free of slip a generating cylinder. This generating cylinder is coupled with the test gear and is provided with an auxiliary drive which can be set or adjusted to a substantially constant torque or rotational moment. There is also provided a final or end measuring velocity setting or adjustment device which delivers the set or reference value for the velocity regulator as well as there being provided a torque or rotational moment setting device for the auxiliary drive.
A state-of-the-art gear testing machine for which there has been provided such control arrangement has been illustrated in FIG. 1, based upon which there initially will be briefly explained the measuring principles of such a gear testing machine or gear tester.
During the profile testing of gears the generating slide or carriage 10 is shifted by an infinitely variable or regulatable profile measuring drive motor 12. By means of the lever system 14 there is thus moved the generating straight edge 16 which is mounted upon ball or spherical guides. A generating cylinder 18 rolls free of slip upon such generating straight edge 16 or equivalent structure. This rotational movement is transmitted by means of a magnetic coupling to a workpiece spindle 20. After the operator has set the base circle diameter at the machine, the lever system 14 is positively altered by the feed or advance slide 22 in such a manner that the produced relative movement between the feeler or probe 24 and the test gear 26 always exactly corresponds to the generating or rolling motion which results due to rolling of the test gear upon its tooth base circle. The relative movement between the feeler 24 and the tooth flank of the test gear 26 therefore exactly corresponds to an involute which coincides with the base circle of the test gear. When the tooth profile deviates from the exact involute shape, then the feeler 24 is correspondingly deflected. The deflection of the feeler 24 is indicated by a not particularly illustrated recording device and is recorded or plotted in accordance with the selected magnification scale.
During testing of the tooth direction the cam disk 28 or the like is rotated by an amount corresponding to the base helix angle, and the vertical slide or carriage 30 is moved by a helix measuring drive motor 32, whereas the generating slide 10 is stationary. Due to the inclined position of the cam disk 28 there is shifted the helix slide or carriage 34, with the result that the lever system 14 again moves the generating straight edge 16 and the test gear 26 is rotated. By virtue of the rotation of the test gear 26 and the vertical movement of the feeler 24 there results a relative movement in the form of a helix or screw line, the pitch of which, related to the base circle cylinder of the test gear, exactly corresponds to the set helix angle. Hence, the feeler 24 moves up and down along a flank line. Each deviation of the tooth flank from the theoretical helix or screw line causes a deflection of the feeler which is indicated by the recording device and is plotted or otherwise registered in accordance with the selected magnification scale.
It has been found that with such gear testing machines or gear testers the required testing accuracy only is attainable for gears up to a diameter of 1.60 meters and up to a weight of about 6 tons. In the case of gears having a larger diameter and a greater weight the entire measuring system becomes so sensitive to vibrations or oscillations that it is no longer possible to accomplish accurate measurements, especially during the starting phase of the measurements performed at each tooth flank. The inertia of the test gear is then so great that during the force transmission from the slide system by means of the lever system and the generating straight edge to the test gear, in order to place such into rotation, there are excited at the machine natural vibrations or oscillations which so falsify the measurement result that such is not usable. With the previously described prior art gear testing machine there is provided an auxiliary drive 36, the rotational moment of which can be set or adjusted, in a manner to be described more fully hereinafter, in such a fashion that, among other things, it compensates for all bearing friction at the region of the workpiece spindle 20. However, during each measuring operation which begins anew at each tooth flank, there arise oscillations or vibrations when testing very large gears, because of the inadequate stiffness or rigidity of the arrangement composed of the lever system and the generating straight edge, which vibrations could not heretofore be avoided with any of the known gear testing machines. The curve 2 in FIG. 2 illustrates such oscillations or vibrations at the beginning of the measuring operation when performing a measurement in a direction from the base or root to the head or tip of the tooth flank. It will be seen that the start-up vibration phenomenon at the beginning of the curve amounts to practically one-tenth of the total measurement; this means that the measurement is practically rendered unusable by virtue of this start-up vibration phenomenon.
In order to circumvent the problem of the oscillation or vibration-sensitivity there has become known to the art from U.S. Pat. No. 3,741,659, granted June 26, 1973, a gear testing machine wherein, instead of the arrangement composed of the lever system and the generating straight edge for rotating the test gear by a rolling or generating motion, there are provided purely electronic means, i.e., there is used an independent drive for the rotational movement of the test gear and for the linear movement of the slide or carriage along with the feeler. The motors provided for the individual movements always operate independently of one another and are mutually synchronized by means of tachogenerators. However, in practice it has been found that the mutual movement coordination requires extremely accurate measuring value transmitters and an expenditure in electronic components which is not economically feasible.
Additionally, there is known to the art a gear testing machine from German Pat. No. 2,747,863, granted April 30, 1981, which generally corresponds to the broad description of gear testing machine of this development heretofore recited at the outset of this disclosure, inasmuch as there is likewise present the mechanical arrangement between the slide system and the test gear. Further, there is provided for the slide or carriage system and the generating cylinder a respective independent or separate drive motor. What is however different is that between the slide system and the generating straight edge of the mechanical transmission train there is arranged a displacement path pickup which detects the relative movements between the slide and the generating straight edge. The output of the displacement path pickup or transducer is connected, on the one hand, with a follow-up regulation device for the drive motor of the measuring slide and, on the other hand, is connected by means of a difference forming device with the feeler. In this case the drive for the test gear does not constitute any auxiliary drive, rather is a primary or main drive which places the test gear into rotation, instead of accomplishing a generating or rolling operation between the generating straight edge and the generating cylinder. Also with this prior art machine oscillation or vibration problems arise during the testing of large gears, in particular always during start-up of the measuring operation at each tooth flank. Additionally, a gear testing machine, where there is provided the usual slide system, the lever system with the generating straight edge and the auxiliary drive for the test gear, is not readily capable of being retrofitted to operate in accordance with the principles of this prior art machine.
The aforementioned oscillations or vibrations--herein sometimes simply referred to as vibrations--which arise during start-up of the measuring drive can be, of course, avoided in the case of gears where the tooth flanks possess a relief, because it is at that location where the start-up operation of the measuring drive occurs, while the feeler or probe is still located at the region of the relief, in other words not at the active tooth flank, and thus, the actual measurement first begins after the start-up vibrations have already ceased. However, most gears do not possess any such type of relief. Additionally, the aforementioned start-up vibrations or oscillations also can be avoided if the measuring drive is started-up over random long time periods. However, that is not a practical solution, because there is demanded of a gear testing machine a certain measuring capacity or efficiency which presupposes that for the measurement of each tooth flank there is not employed more time than is absolutely necessary. It is therefore necessary that valid measurement results are available as quickly as possible already during the start-up of the measuring drive, i.e., during its run-up to the final or end measuring velocity.